Sensor for belt retractor

Abstract

A sensor for a vehicle belt retractor includes a housing, an excitation mass, a locking mechanism which locks the belt retractor, and a lever arm connected to the housing. The lever arm is in contact with the excitation mass and engages the locking mechanism when the excitation mass moves relative to the housing. The sensor further includes a damper that restricts vertical displacement of the excitation mass relative to the housing.

1. A sensor for a seat belt retractor for a vehicle comprising:
 a housing; 
 an excitation mass that is displaceable relative to the housing in response to inertial forces acting on the vehicle; 
 a lever arm connected to the housing at a pivot point, the lever arm contacting the excitation mass upon a predetermined displacement of the excitation mass in response to the inertial forces and causing locking of the seat belt retractor upon the predetermined displacement of the excitation mass; and 
 a damper that restricts vertical displacement of the excitation mass relative to the housing thereby restricting undesired locking of the seat belt retractor, the damper not restricting displacement of the excitation mass in response to the inertial forces acting on the excitation mass causing displacement in directions other than in the vertical direction. 
 
   
   
     2. The sensor of  claim 1  wherein the excitation mass is a spherical mass. 
   
   
     3. The sensor of  claim 1  wherein the housing is provided with an indentation in which the excitation mass resides when the inertial forces are not acting on the vehicle. 
   
   
     4. The sensor of  claim 3  wherein the indentation is defined in part by an inclined surface, wherein displacement of the excitation mass relative to the housing includes a movement over the inclined surface. 
   
   
     5. The sensor of  claim 1  wherein the lever arm is provided with a hole through which the damper extends. 
   
   
     6. The sensor of  claim 1  wherein the excitation mass is a non-spherical mass that pivots about a point defined by the housing. 
   
   
     7. The sensor of  claim 6  wherein the excitation mass moves the lever arm away from the point as the excitation mass pivots about the point. 
   
   
     8. The sensor of  claim 1  wherein a gap exists between the lever arm and the excitation mass when the inertial forces are not acting on the vehicle. 
   
   
     9. The sensor of  claim 8  wherein displacement of the excitation mass closes the gap. 
   
   
     10. The sensor of  claim 8  wherein displacement of the excitation mass relative to the housing defines a no lock zone when the gap is greater than zero, the retractor being unlocked when the excitation mass occupies the no lock zone. 
   
   
     11. The sensor of  claim 8  wherein the movement of the excitation mass relative to the housing defines a lock zone when the excitation mass undergoes the predetermined displacement and excitation mass contacts the lever arm, the retractor being locked when the excitation mass occupies the lock zone. 
   
   
     12. The sensor of  claim 1  further comprising one or more additional dampers for restricting vertical displacement of the excitation mass. 
   
   
     13. The sensor of  claim 12  wherein at least one of the additional damper provides opposing magnetic fields.